1. Field of the Invention
This invention relates to seals, and more particularly, to security seals of the type that have a housing connected to a strap member having an end which is received within the housing and locked therein. The primary purpose of the seal is to prevent unauthorized opening thereof by any means which would not be readily detectable.
2. Description of the Prior Art
Shackle seals have become well-developed over the years. They are in wide-spread use for security sealing the doors in cargo trucks and the like. Among the requirements for them are that they be easy to use, that they function adequately and that they be inexpensive. The one-piece plastic seal has become the shackle seal of choice in most instances. Such seals are easy to stock, non-corrodible, easy to place in service, and easy for the authorized person to break and dispose of at the appropriate time.
Since truck cargos are valuable and subject to pilferage, such seals must be strong enough to withstand ordinary handling and not subject to inadvertent breakage. Of special importance is that their structure be such that they may not be opened and reclosed without evidence of such opening being apparent.
The use of a shackle housing having internal spring fingers which engage the end portion of the shackle has become well known. In order for such housing to be secure against tampering, it is necessary that both of its ends be closed to prevent the insertion of a pointed, manipulating instrument. Due to the internal structure of the housing, it is not economically feasible to manufacture the same with one of its ends closed.
Attempts have been made to provide a closure for the end of the housing by an added step of molding over an end portion following the initial molding. Examples are shown in Moberg et al. U.S. Pat. Nos. 4,059,300 and 3,466,077.
A plug connected to a tab on the housing is disclosed in Harley U.S. Pat. No. 3,954,295.
The Guilar U.S. Pat. No. 4,229,031 discloses a plug for a housing in which the plug has a pair of legs which compress inwardly when the plug is inserted into the housing. The Moberg U.S. Pat. No. 4,319,776 is somewhat similar.
Another example of a cap member for a plug is disclosed in Chevillard et al. U.S. Pat. No. 4,609,218.
The Fuehrer U.S. Pat. No. 3,712,655 discloses a shackle seal having indentations in the strap to provide an appropriate level of breaking. The patent to Harley, above mentioned, also discloses an opening 50 in its strap for the purpose of facilitating breakage and an oval base in its housing to prevent rotation of the end portion 12.
The Paradis U.S. Pat. No. 4,559,676 discloses a tip member for a shackle seal which has a portion that is compressed when it is inserted into the locking head.